It's easy to simply follow the directions on recipes. You heat up your oven to a certain temperature, pop in your food, and walk away. However, as Slate points out, oven temperatures are not an exact science. In fact, they're usually well off the mark and shouldn't be trusted at all.

Essentially, when you turn your oven to 350 degrees, that doesn't mean your oven is going to be 350 degrees. The heat will likely surge between around 330 and 370 degrees if it's calibrated correctly. To correct for this, you'd think a thermometer would work, but it doesn't:

[U]nless your thermostat is consistently and significantly off in the same direction, the variability in temperature throughout the chamber makes this trick pretty useless. Obsessives have their ovens professionally recalibrated annually, but this does nothing to address the temporal and spatial fluctuations of heat that are features of how ovens work.

So, your oven can't really regulate temperature, and a thermometer isn't going to help much. What do you do? You need to learn how to tell when your food is really done:

[Y]ou could give up on the numbers, and follow [New York Times food columnist, Mark] Bittman's advice: "Cooks should get used to the visual and olfactory (and even aural) cues that food gives off while it's baking or roasting." And if you're not confident enough to trust your eyes, nose, and ears, use a thermometer-not the kind that sits inside your oven, but the kind you stick in the food as it's cooking. "The instant-read thermometer, used frequently, solves most issues," says Bittman.

Keeping an eye on you baking food isn't a new idea, but if you're the type to set-it-and-forget-it with your oven, it might be time to start paying closer attention. Head over to Slate for a short history of ovens, and details on how food makers come up with baking directions in the first place.